Package strapping tool

ABSTRACT

In a strapping tool of the kind in which a knurled rotary dog is urged into frictional engagement with the face of one end of a loop of metal strapping and rotated to tighten the loops around a package, overlapping ends of the loop then being secured by jointing means in the tool, the inclusion of means for sensing the bodily movement of the rotary dog in compressing and penetrating the strapping as an indication of the tension in the loop. When a predetermined bodily movement of the rotary dog has occurred the sensing means causes or allows the jointing means to secure the ends of the loop.

United States Patent 1 1111 3,929,172 Sansum Dec. 30, 1975 PACKAGE STRAPPING TOOL 2,682,150 6/1954 Ballinger /374 3 41 4 A l 140 93.4 Inventor: Robert David Sansum, Harpenden, H9 ngam a E l d i an Primary ExaminerLowell A. Larson [73] Ass1gnee: Gerrard Industries Limited, Attorney, Agent, or Firm Kemon, Palmer &

Rotherham, England Estabrook [22] Filed: June 5, 1974 21 Appl. No.2 476,446 [57] ABSTRACT 1. In a strapping tool of the kind in which a knurled rotary dog is urged into frictional engagement with the [30] Forelgn Application Pnomy Data face of one end of a loop of metal strapping and ro- May 3], United t t d t the loops around a package overlap.

ping ends of the loop then being secured by jointing [52] US. Cl. /93.2 means i th t th incl sion of means f0! sensing [51] Int. Cl. B21F 9/02 the bodily movement f h rotary d in ompressing [58] Field of Search 140/932, 93.4; 254/51; and penetrating the strapping; s an indication of the 60/374382 tension in the loop. When a predetermined bodily movement of the rotary dog has occurred the sensing [56] References Cited means causes or allows the jointing means to secure UNITED STATES PATENTS the ends of the loop. 2,391,996 H1946 Muller 60/382 2,545,051 3 1951 Schutt 60/382 9 Clams 4 Dramng guns 1 12 O --I\\ P 3 6 US. Patent Dec.30, 1975 Sheet10f4 3,929,172

TOE

US. Patfint Dec. 30, 1975 Sheet 2 of4 3,929,172

US. Patent Dec. 30, 1975 Sheet 3 of4 3,929,172

US. Patent Dec.30, 1975 Sheet40f4 3,929,172

PACKAGE STRAPPING TOOL This invention relates to strapping tools of the kind comprising jointing means for securing together the overlapping ends of a loop of strapping which has been tightened around a package and tensioning means including a knurled rotary dog which is urged into frictional engagement with the face of one end of the loop of strapping and rotated to tension the loop. Such strapping tools are hereinafter referred to as being of the kind defined.

Some strapping tools of the kind defined are entirely hand-operated, others are entirely power-operated, usually pneumatically or hydraulically. Still others are operated partly by hand and partly by power. For example, the tensioning means is sometimes poweroperated but the means for making the joint securing together the overlapping ends of the joint is operated by hand or, alternatively, the tensioning means is handoperated and the jointing means power-operated.

In most strapping tools of the kind defined it is possible to make the joint before sufficient tension has been applied to the loop and it is an object of the present invention to provide means for preventing this.

The present invention consists in a strapping tool of the kind defined comprising sensing means, responsive to bodily movement of the rotary dog having at least a component in a direction normal to the strapping and towards a support on the far side of the strapping, for initiating or permitting the making of the joint by the jointing means when such movement exceeds a predetermined amount.

The bodily movement of the rotary dog is indicative of the force with which the rotary dog is urged against the strapping and, usually, of the depth to which the knurling of the rotary dog has penetrated the strapping. In strapping tools of the kind defined this movement normal to the strapping is a function of the tension applied to the strapping since the higher the tension in the strap produced by friction between the rotaty dog and the strapping, the greater must be the force normal to the strapping to produce the frictional force and the greater the resulting compression or penetration of the strapping.

The sensing means may actuate a valve or switch to initiate the making of the joint by power-operated jointing means or it may release a catch or interlock otherwise preventing the use of a power or manuallyoperated jointing means.

The support will usually be rigid with the body of the tool but this is not essential. It may directly engage the far side of the end of the loop of strapping which is engaged on the near side by the rotary dog or it may be on the far side of the more remote of the overlapping ends of the loop. A pressure plate may be interposed between the overlapping ends of the loop at the position where they are gripped between the rotary dog and the support. Alternatively the overlapping ends may be in direct contact with one another.

In one form of the invention the rotary dog is carried by an angularly movable arm affording movement of the rotational axis of the rotary dog mainly towards and away from the strapping and it is the angular movement of the arm to which the sensing means is responsive. In this example the sensing means comprises a lever which is picked up by the arm after a pre-determined angular 2 movement and moved to initiate or permit the operation of the jointing means.

The sensing means preferably includes means for amplifying the small movement due to compression or penetration of the strapping to facilitate initiation of the operation of the jointing mechanism or the release of means preventing its operation.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a front elevation,

FIG. 2 is an end elevation,

FIG. 3 is an enlarged view, partly in section, of part of FIG. 1, and

FIG. 4 is a sectioned view on line 44 of FIG. 1.

The strapping tool illustrated. in the drawings is based on that described in British P'atent Specification No. 1,331,221 and comprises a body, including a base plate 1 and a housing 2 for jointing means in the form of a punch and die assembly 3, a pneumatic ram assembly 4 for operating the punch and die assembly 3, an air motor assembly 5 for tensioning a metal strap 6 to be fastened around a package, and a control valve assembly 7 by which the operation of the strapping tool is controlled.

The jointing means produces ajoint of the seal-less type in overlapped portions of metal band strapping.

The air motor assembly 5 comprises an air motor 8 which drives a knurled wheel or rotary dog 9. The rotary dog 9 is disposed over a pressure plate 10 which is secured to and lies over the base plate 1 against which it is urged by spring means. For inserting the strap 6 the rotary dog 9 is held away from the pressure plate by a catch (not shown) released by an arm 34 (FIG. 2).

The air motor assembly 5 is pivotally connected to the housing 2 about a pivot 11 so that the rotary dog 9 is movable towards and away from the pressure plate 10. An outrigger bracket 12 is also pivoted about the pivot '11 and has an outer bearing for supporting the rotary dog 9. An auxiliary ram assembly 13 having a piston rod 14 is pressurised whenever compressed air is applied to the air motor assembly 5 and the piston rod 14 urges the air motor assembly 5 about its pivot 11 so that the rotary dog 9 is forced towards engagement with the pressure plate 10.

The control valve assembly 7 comprises spool valves 15 and 16 (FIG. 4). Both valves are normally closed. The valve 15 is the tension valve. It controls the air supply to the air motor assembly 5 and the auxiliary ram assembly 13 and is openable by depressing a tension valve lever 17.

The valve 16 is the jointing valve and controls the air supply to the pneumatic ram assembly 4. The valve 16 is actuated by a piston 18 in a. slave cylinder 19. The piston 18 carries a pin 20 which projects through a slot in the wall of the slave cylinder to bear on the tension valve lever 17 and hold it depressed when the piston 18 moves down.

An upward extension 35 of the outrigger bracket 12 overlaps a shoulder 21 of an arm 22 pivoted to the housing. The free upper end of the arm 22 carries an adjusting screw 23 the tip 33 of which, as best seen in FIG. 3, is in line with one end of a poppet valve spool 24 slidable in a chamber 25 in the housing 2 and controlling the supply of air to the slave cylinder 19. The shoulder 21 is much nearer the pivotal axis of the arm 22 than is the adjusting screw 23 so that bodily move- 3 ment of the rotary dog 9 occurring after engagement of the extension. 35 with the shoulder 21 is amplified. The arm 22 and screw 23 constitute sensing means responsive to bodily movement of the rotary dog 9.

The air supply reaches the chamber 25 by an inlet port 26. The spool 24 is spring biased to urge a disc 28 onto a seating around the inner end of the chamber 25 so preventing air from passing to outlet ports 29 open to a passage 30 leading to the top of the slave cylinder 19. The spool 24 has a central bore 31 open at the inner end through a port 36 to that part of the chamber from which the outlet ports 29 open. The outer end of the bore 31 is open to the atmosphere and forms an exhaust port. Around the outer end of the bore 31 is an annular seal 32 against which the tip 33 of the adjusting screw 23 bears to close the bore 31 and move the spool 24.

The spool valve 24 constitutes a pilot valve of an auxiliary fluid-pressure system including the slave cylinder 19 and piston 18 actuating a main valve formed by the valve 16.

In use of the tool, the free end of a length of strapping 6 is clamped between the pressure plate and the base plate 1 with the strapping extending to the left, as viewed in FIG. 1. The strapping is formed into a loop around the package and the other end of the loop is inserted between the rotary dog 9 and the pressure plate 10. The rotary dog 9 is then released by operation of the arm 34 (FIG. 2) to clamp the strapping against the pressure plate 10.

When the operator presses the tension valve lever 17 the air motor 8 rotates the rotary dog 9 clockwise to draw in the loop of strapping around the package. The auxiliary ram 13 urges the rotary dog 9 against the strapping with greater force as the tension in the strapping causes greater resistance to the driving force of the air motor 8 with a consequent rise in the air pressure at the air inlet to the tool. Finally, at a pre-determined pressure, the air motor 8 stalls and at this maximum air pressure the force with which the rotary dog 9 bears on the strapping is at its greatest. The resulting penetration or compression of the strapping by the rotationally-stationary knurled surface of the rotary dog 9 causes the extension 35 of the outrigger bracket 12 to reach its furthest anti-clockwise position (as viewed in FIGS. 1 and 3). In reaching this position the extension 35 has engaged the shoulder 21 and moved the lever 22 in a clockwise direction to cause the pointed end of the adjusting screw 23 to close the central bore 31 of the spool 24 and move the spool 24 to the right. This admits air to the slave cylinder 19 and initiates the operation of the jointing mechanism by the ram assembly 4. As previously mentioned, at this stage the tension valve lever 17 is held down by the pin so that the supply of compressed air to the air motor 8 is maintained even if the operator releases the tension valve lever 17.

When the jointing operation is completed and the jointing mechanism has severed the strapping between the jointing mechanism and the rotary dog 9, the rotary dog 9 rotates freely (since there is no longer any tension in the strap) the air pressure on the auxiliary ram assembly 13 falls allowing the rotary dog 9 to rise. The adjusting screw 23 moves to the left (as viewed in FIGS. 1 and 3) and is followed by the spool 24 until the disc 28 seats shutting off the air supply. The tip 33 of the adjusting screw 23 moves away from the end of the spool 9 opening the end of the bore 31 to allow air to 4 escape from the slave cylinder 19 and its piston 18 to return to its starting position.

As the tool relies upon the depth of penetration or compression of the rotary dog 9 into the strapping rather than a rise of air pressure to initiate the operation of the jointing mechanism, by proper adjustment the tool can be arranged to make the joint only after the air motor has stalled. This is desirable to allow time for the package and strap to consolidate with consequent smaller variations in tensions between packages.

Except for the modifications described herein the strapping tool is as described in British Patent Specification No. 1,331,224 to which reference should be made for further details which however form no part of the present invention.

I claim:

1. A strapping tool of the kind comprising jointing means for securing together the overlapping ends of a loop of strapping which has been tightened around a package and tensioning means including a rotary dog and a support opposite the rotary dog, in use at least one end of a loop of strapping being disposed between the rotary dog and the support, the rotary dog being urged into frictional engagement with the face of said one end of the loop of strapping and rotated to tension the loop wherein the strapping tool further comprises sensing means responsive to bodily movement of the rotary dog having at least a component in a direction normal to the strapping and towards the support, for initiating or permitting the making of the joint by the jointing means when such movement exceeds a predetermined amount.

2. A strapping tool according to claim 1 wherein the rotary dog is carried by an angularly movable arm affording movement of the rotational axis of the rotary dog mainly towards and away from the strapping, the sensing means being responsive to the angular movement of the arm.

3. A strapping tool according to claim 2 wherein the sensing means comprises a lever which is picked up by the arm after a pre-determined angular movement of the arm and moved to initiate or permit the operation of the jointing means.

4. A strapping tool according to claim 1 wherein the sensing means includes means for amplifying the small movement due to compression or penetration of the strapping to facilitate initiation of the operation of the jointing means or the release of means preventing its operation.

5. A strapping tool according to claim 1 and further comprising fluid pressure means for operating the jointing means and including a main valve and an auxiliary fluid pressure system actuating the main valve, the auxiliary fluid pressure system including a pilot valve actuated by the sensing means.

6. A strapping tool according to claim 5 wherein the auxiliary fluid-pressure system includes a slave piston and cylinder assembly for actuating the main valve.

7. A strapping tool according to claim 1 comprising a fluid pressure motor driving the rotary dog, a fluidpressure means for operating the jointing means and a manual control governing the admission of fluid pressure to the motor, means being provided for maintaining the admission of fluid pressure to the motor if actuation of the manual control is discontinued after initiation of the operation of the jointing means by the sensing means.

6 the jointing means.

9. A strapping tool according to claim 5 wherein the pilot valve is a spool valve having an exhaust port at one end closable by part of the sensing means by which the spool valve is also movable axially to cause the auxiliary fluid-pressure system to actuate the main valve. 

1. A strapping tool of the kind comprising jointing means for securing together the overlapping ends of a loop of strapping which has been tightened around a package and tensioning means including a rotary dog and a support opposite the rotary dog, in use at least one end of a loop of strapping being disposed between the rotary dog and the support, the rotary dog being urged into frictional engagement with the face of said one end of the loop of strapping and rotated to tension the loop wherein the strapping tool further comprises sensing means responsive to bodily movement of the rotary dog having at least a component in a direction normal to the strapping and towards the support, for initiating or permitting the making of the joint by the jointing means when such movement exceeds a pre-determined amount.
 2. A strapping tool according to claim 1 wherein the rotary dog is carried by an angularly movable arm affording movement of the rotational axis of the rotary dog mainly towards and away from the strapping, the sensing means being responsive to the angular movement of the arm.
 3. A strapping tool according to claim 2 wherein the sensing means comprises a lever which is picked up by the arm after a pre-determined angular movement of the arm and moved to initiate or permit the operation of the jointing means.
 4. A strapping tool according to claim 1 wherein the sensing means includes means for amplifying the small movement due to compression or penetration of the strapping to facilitate initiation of the operation of the jointing means or the release of means preventing its operation.
 5. A strapping tool according to claim 1 and further comprising fluid pressure means for operating the jointing means and including a main valve and an auxiliary fluid pressure system actuating the main valve, the auxiliary fluid pressure system including a pilot valve actuated by the sensing means.
 6. A strapping tool according to claim 5 wherein the auxiliary fluid-pressure system includes a slave piston and cylinder assembly for actuating the main valve.
 7. A strapping tool according to claim 1 comprising a fluid pressure motor driving the rotary dog, a fluid-pressure means for operating the jointing means and a manual control governing the admission of fluid pressure to the motor, means being provided for maintaining the admission of fluid pressure to the motor if actuation of the manual control is discontinued after initiation of the operation of the jointing means by the sensing means.
 8. A strapping tool according to claim 7 comprising in the fluid pressure means a main valve and an auxiliary fluid pressure system including a slave piston and cylinder assembly actuating the main valve, the auxiliary fluid pressure system comprising a pilot valve actuated by the sensing means and the slave piston and cylinder assembly including means for holding the manual control actuated when the slave piston and cylinder assembly is in the condition for operation of the jointing means.
 9. A strapping tool according to claim 5 wherein the pilot valve is a spool valve having an exhaust port at one end closable by part of the sensing means by which the spool valve is also movable axially to cause the auxiliary fluid-pressure system to actuate the main valve. 